To determine the efficacy of Temozolomide defined as progression-free survival at 6 months and safety of Temozolomide when administered orally, once a day for 5 days repeated every 28 days in the treatment of patients with GBM (Glioblastoma Multiforme) or AA (Anaplastic Astrocytoma) at first relapse. A reference agent procarbazine is included in the study of patients with GBM to verify that objective responses can be obtained using the reference agent.